Round Up A Number to the Greatest 10s Place

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Recently, we faced a situation in which we need to round up a number to the greatest 10s place.

For example: we needed to round up a number as follows:

• 1023     -> 2000
• 37911   -> 40000
• 912345 -> 1000000

First, we checked Math.Round(). But it didn’t solve our problem. Math.Round() supports only rounding a value to the nearest integer or to the specified number of fractional digits. On further checking, we come up with a solution by using Math.Ceiling() method.

Math.Ceiling() returns the smallest integral value that is greater than or equal to the specified double-precision floating-point number.

For example:

• Math.Ceiling(7.3)   -> 8
• Math.Ceiling(7.64) -> 8
• Math.Ceiling(0.12) -> 1

Below is the solution we came up with:

decimal[] values = { 1023, 37911, 23000, 1234, 912345 };
foreach (var value in values) {
//// get the length of the 10s places;
var length = value.ToString().Length - 1;
//// using Math.Pow() calculate the power of 10s
var power = Math.Pow(10, (double)length);
//// var roundadValue = Math.Ceiling(1023 / 1000) * 1000;
var roundadValue = Math.Ceiling(value / (decimal)power) * (decimal)power;

Console.WriteLine("Value:{0} Rounded Value:{1}", value, roundadValue); 
}

The Logic

Math.Ceiling(value / (decimal)power) * (decimal)power;
var roundadValue = Math.Ceiling(1023 / 1000) * 1000;

So, for any number, first calculate the power of 10s and then use it for the above calculation to get the results.